This invention relates to a process for the high pressure grouting within the earth, and an apparatus adapted for carrying out same.
Before initiating the grouting process, it is naturally necessary to dig or bore mechanically or hydro-mechanically a vertical hole into the earth. It is known to construct sand seams and solidified bodies such as watertight walls by the so-called chemical grouting after digging, crushing, piercing and injecting with high-velocity jets of liquid such as water discharged from nozzles. High-velocity liquid jets are utilized in various construction techniques known as jet grouting, sand draining, jet piling, etc. These methods are effectively used because they are high in digging efficiency, provide high energy-density rates and require but a relatively small and simple device for producing high-velocity liquid jet. It is usually in the stratus with subterranean water or at the sea floor that high-velocity liquid jets are used for piercing and crushing. The water encountered in such locations rapidly slows down the velocity of jet liquid to reduce the working efficiency of the jet. Specifically, the in-water distance that the liquid jet can traverse ranges from about 1/10 to 1/15 of the in-air distance that the jet can traverse. This accounts for the inability of a high-velocity liquid jet to perform well when the jet of liquid is directed into a zone of water.
In order to increase the in-water distance that the high-velocity liquid jet traverses, it has been proposed in the prior art that an air jet be discharged from a ring-shaped nozzle surrounding the liquid jet nozzle so that the air jet will envelop the high-velocity liquid jet. Devices implementing this proposition have been successful in increasing the distance traversed by high-velocity liquid jets in water and, moreover, the air jet was noted to facilitate removal of loosened or crushed sand or the like because of its air lifting effect. An example of such a practice known in connection with jet grouting is disclosed in U.S. Pat. No. 3,802,203 which is incorporated herein as a known reference. In this known technique, a pair of coaxial jet nozzles is provided for supplying two liquid chemicals. We have experienced that with such known technique, the invading distance of these liquid jets is rather limited.
Even with a high-velocity liquid jet enveloped by air jet, a drawback has been noted in that there are fluctuations in the distance traversed by the liquid jet, termed the liquid jet distance in this specification, thus introducing discontinuous portions in watertight wall construction, or producing an anisotropic or non-homogeneous deposition of the cementing agent in solidifying work.
It is an object of the invention to provide an improved process for chemical grouting wherein the liquid jet-piercing distance into the earth is substantially improved for the purpose of enlarging the grouting zone.
It is a further object to provide an improved process of the above kind providing a possibility for solidifying the jet-crushed earth masses, even with use of common cement milk in place of the high price resin base solidifier.
It is a further object to provide a high efficiency and low cost process of the above kind over the known prior art.
These and further objects, features and advantages of the invention will become more apparent when read the following detailed description of the invention to be set forth with reference to the accompanying drawings.